1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. Further, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a memory device, an arithmetic device, an imaging device, a driving method thereof, or a manufacturing method thereof.
2. Description of the Related Art
In recent years, self-luminous display devices, light-emitting devices, and the like including light-emitting elements such as electroluminescence (EL) elements in pixels have attracted attention. As examples of such a light-emitting element used in such a self-luminous display device, an organic EL element and an inorganic EL element are known. These light-emitting elements emit light by themselves; thus, the visibility of an image displayed by a display device including the organic EL element or the inorganic EL element is higher than that of an image displayed by a display device including a liquid crystal element. Further, the organic EL element and the inorganic EL element have advantages such as unnecessity of a backlight and high response speed.
An organic EL element has a structure in which a layer containing a light-emitting organic compound (hereinafter referred to as an EL layer) is sandwiched between a pair of electrodes. Light emission can be obtained from the EL layer when voltage is applied between the pair of electrodes. Patent Document 1 discloses an example of a display device including such an organic EL element.